These were bittersweet tears, borne of hope. They are warm memories compared with the years of emotional torment that followed.

The losing. The lawsuits. The humiliation. The blown draft picks. The foolish trades. The false promise of Isiah Thomas. The petulance of Stephon Marbury. The feckless leadership of James Dolan. The callous dismissal of Jeremy Lin.

When the Nets have their delayed opening of the season on Saturday night, Ortiz will be draped in black and white — a proud, newly converted fan of the transplanted Brooklyn team.

“I was rubbed the wrong way for so long,” said Ortiz, who lives in Bay Ridge, “that I guess I was kind of looking for an out.”

A new era is upon us. The Nets are a New York team now, after 35 years in New Jersey. Their arrival has spawned a new breed of fan: the Knicks-to-Nets defector. They are the disillusioned, the angry, the hopeful. And their numbers appear to be growing, based on social media and anecdotal accounts.

Find a fan who switched teams, and he will tell you about three others who have done the same: a brother, a girlfriend, a co-worker. Many are Brooklyn natives who are thrilled to root for a Brooklyn team. But the defectors say they were driven away, by the same grievances that Knicks fans have been reciting for years.

“I don’t want to take this parallel too far, but it was like an abusive relationship,” said James Graham, a Prospect Heights resident who renounced his Knicks fandom. “I got out.”

There is no Gallup Poll for team allegiance, so the trend is hard to quantify. Nets officials say they are not keeping track. But this much is known: The Nets have sold nearly 11,000 full-season tickets, triple the number from last season. Most are coming from Brooklyn (37 percent), Manhattan (23 percent) and Nassau County (6 percent).

It is doubtful they all became basketball fans overnight, or were closet Nets fans all along. It is more likely that a great number are, in fact, Knicks apostates, who are making Mikhail Prokhorov, the Nets’ brash owner, look positively prophetic for declaring in 2010, “We’re going to turn Knick fans into Net fans.”

Of course, Prokhorov had lots of help, mostly from the Knicks. Few teams in the last decade have tortured their fan base as relentlessly, with a toxic brew of bad basketball, bad characters and bad karma.

Photo

James Graham, 41, is a Prospect Heights resident who switched his allegiance from the Knicks to the Nets.Credit
Yana Paskova for The New York Times

The Knicks have not won a playoff series since 2000. They have had a losing record in 9 of the last 11 seasons, compiling a record of 357-529. They have been sued for sexual harassment and picketed by fans. Last season, a dispute between Madison Square Garden and Time-Warner Cable left thousands of viewers without Knicks games. That came just months after the team raised ticket prices by an average of 40 percent.

Dolan, the Garden chairman, might be the most reviled figure in New York sports.

“The only thing that would make me go back is if they sold the team,” said Brian Dowling, a 35-year-old defector who lives in Long Island. “I don’t think it will happen anytime soon.”

Dowling added, “At a certain point, I just asked myself: Is this worth it?”

Knicks fans have been asking this existential question for years, to no productive end. Who else could they root for? The Chicago Bulls? Impossible. The Boston Celtics? Unconscionable. The team in New Jersey? Meh.

But, reborn in Brooklyn, the Nets now exude cool. They have the sleek black uniforms, the imprimatur of Jay-Z and the billion-dollar arena. With an All-Star backcourt and a promising core, the Nets present a worthy alternative to fans across the region, but especially to the 2.6 million people who call Brooklyn home.

“It’s a unique phenomenon, and it’s a unique opportunity,” said Graham, 41, who lives five blocks from Barclays Center.

Graham grew up on that same street, a devout Knicks fan. He idolized Patrick Ewing, agonized over Bernard King and got his heart broken by Michael Jordan. He was at the Garden on May 7, 1995 — the day that Indiana’s Reggie Miller scored 8 points in 9 seconds to beat the Knicks in a playoff game.

“I didn’t make the switch lightly,” Graham said. “I was a loyal fan for a long, long time. And that loyalty, now that it’s been pried away with a crowbar, now it’s attached to a new team.”

The defectors all describe a similar evolution.

They were depressed by the Thomas-Marbury era. They were heartened by the 2008 arrival of Donnie Walsh and Mike D’Antoni — as the new team president and coach — then distressed to see both men run off. They embraced Amar’e Stoudemire as the foundation of a promising new lineup in 2010. They cringed when that lineup was torn up in a hasty trade for Carmelo Anthony.

If there was a catalyzing event in this movement, it came July 17. That was the day the Knicks chose to let Lin — their inspiring, crowd-pleasing young point guard from Harvard — leave for Houston, rather than match a three-year, $25 million contract. To many fans, it was the ultimate slap in the face. Lin had provided more thrills and joy in a two-week span than any Knicks player had in the last 10 years. He was more popular than Stoudemire, more beloved than Anthony.

In the days that followed, Twitter timelines and fan forums were filled with wails of betrayal and outrage, and threats to abandon the team. Many followed through. Many swallowed their rage, maintaining their Knicks allegiance in spite of themselves.

“Every rational part of my brain wants to be a Nets fan,” said Brian Koppelman, a Knicks season-ticket holder since 1989.

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"I was rubbed the wrong way for so long that I guess I was kind of looking for an out."Nelson Ortiz, a longtime Knicks fan who is now a converted fan of the transplanted Brooklyn teamCredit
Yana Paskova for The New York Times

“My very first memory I have when I was 4 years old is me and my dad at the Garden watching the Knicks,” Koppelman said. “When I close my eyes and think of the Knicks, I still see Earl Monroe.”

So while Koppelman says that the current Knicks’ ownership “deserves to be abandoned” and “deserves to be pilloried,” it is history that keeps him coming back. This is the Knicks’ eternal advantage, and it is the reason team officials have projected unwavering ambivalence — even arrogance — about the Nets’ encroachment on their territory. The Knicks have the legendary names, the storied arena, the two championship banners hanging in the rafters. But the Knicks have been living off the fumes of that legacy for decades now. The last banner was hung in 1973. The charm is fading.

The Knicks still have Woody Allen and Spike Lee (who is staying faithful despite his Brooklyn roots) in their corner. But other celebrities have joined the defector movement. The actress Ellen Pompeo, who had been a semiregular at Knicks games, now has Nets season tickets. The filmmaker Edward Burns has also embraced the Nets (but says he still supports the Knicks, too).

Other notable Nets supporters include the rappers Fabolous and Busta Rhymes, the R&B singer Ne-Yo, the actress Rosie Perez, the actor Michael K. Williams and the pop star Justin Bieber, who wore a “Hello Brooklyn” Nets shirt on the Jimmy Fallon show.

Then there is Ethan Hawke, who in an interview with Spike TV said he felt “completely betrayed and abandoned by the way the Knicks management handled Jeremy Lin.” Hawke said the Knicks were “in my DNA,” but that he planned to take his son to Nets games this season and would re-evaluate his loyalties.

For now, the Knicks still have a sizable edge in fan support, including a two-to-one advantage in Brooklyn, according to Dan Migala, a partner at Property Consulting Group, a Chicago-based sports marketing firm.

About 24 percent of Brooklyn residents either watched, attended or listened to a Knicks game last season, said Migala, citing data provided by Scarborough Sports Marketing. By comparison, 12 percent of Brooklyn residents watched, attended or listened to a Nets game, a difference of about 250,000 people.

But those figures were based on a Nets team based in New Jersey, not one playing with “Brooklyn” across the chest. To those who live in the borough, that makes all the difference.

“Wherever I go in the world, I don’t say I’m from New York,” Ortiz said. “I say I’m from Brooklyn, and people understand that.”

Though Thursday’s meeting between the two teams was delayed in the wake of this week’s storm, the rivalry will eventually be settled on the court. When the moment comes, Knicks fans are vowing to take over Barclays Center, just as they did for years in New Jersey.

“I hope not,” said Ortiz. “But if they do, I hope they leave crying.”

It wouldn’t be the first time.

A version of this article appears in print on November 1, 2012, on page B11 of the New York edition with the headline: Fans in Brooklyn Have New Shoulder to Cry On. Order Reprints|Today's Paper|Subscribe